Could lactose intolerance be in our genes?Comment on this story
London - When archaeologists investigated two 7 000-year-old corpses unearthed in Spain in 2006, they made two startling discoveries.
One of the two Mesolithic hunter-gatherers had carried African and European genes, which meant he had dark skin and blue eyes. But there was an even more amazing revelation from the scientists when they announced the results of their research last month.
The man’s genes also showed he was lactose intolerant.
This is a condition in which the body has difficulty in absorbing the sugar that is commonly found in milk.
A problem drinking milk? What sort of hunter-gatherer was this? Surely food intolerances are a bit modern and namby-pamby?
Well, I can identify strongly with this Mesolithic milk dodger, as I too suffer from lactose intolerance. I’m one of the estimated three million people in the UK for whom a glass of cow juice is about as welcome as being force-fed cod liver oil.
Much to my regret, I only discovered that I had the condition last year, when I was going on a punitive three-day hike through the Yorkshire Dales with a good friend. At one point, as we were puffing up a particularly strenuous climb, he turned to me and observed, “You do realise that you burp ALL the time?”
At first, I was in denial. Surely everybody burps a lot? Maybe I was just bad at hiding it. But by the time we reached the peak, I started to wonder - not least for the sake of my friendship - whether I did have something wrong with me. What happened next was like something out of a film, albeit one that goes straight to video.
On a distant dale, I saw some cows. There they were, munching away, and the sight of them suddenly made me realise: Of course, it was milk. Wretched milk.
Until then, I had dismissed people who claim to have intolerances as being vain and self-important. I’m not talking about those with allergies, which are clearly serious, and can be life-threatening. I’m referring to those annoying people who carp on about being intolerant to this and that, when they are in fact just fussy eaters.
But it was time to confront my prejudices. I was going to give up milk. No more breakfast cereal, no more milk in my tea and coffee. The idea of giving up my cherished daily bowl of Grape Nuts seemed appalling, but I had to give it a try.
Within about two days, my belching had almost vanished. There was no more effervescence, my guts no longer painfully bloated with gas.
There was no doubt that milk was the culprit.
I had cracked it, although I did curse that I had not kicked the milk churn decades before. All those years of subjecting friends and family to constant burping, all that discomfort needlessly endured, and all because I hadn’t tolerated those with intolerances.
Initially, I kept quiet about the whole business, as I didn’t want to be a dietary bore. And then I came across the startling fact that 75 percent of the world has some degree of lactose intolerance. It was another cow-on-a-distant-dale moment. Hang on, I thought, you people who can drink milk, it’s you who are the weird ones! Not me, I’m the normal one.
As it turns out, the ability to tolerate lactose is really only found in people in northern Europe, North America and in pockets in the Middle East and western and southern Africa. If you go anywhere else, you’ll find that everybody is like me and Mesolithic Man.
Why is this? The answer lies in the enzyme lactase, which breaks down the lactose in milk. Although all of us are born with lactase, after about the age of two, the levels in our small intestines diminish rapidly for most people, which makes it hard for lactose to be broken down, and therefore causes discomfort, which is often manifested by burping.
But in countries such as the UK, a genetic mutation in the majority of the population means that lactase persists, and therefore the ability to drink milk can be enjoyed for many decades after infancy.
Last month, British scientists who have studied the residue in cooking pots from archaeological digs estimated that this mutation may have taken place 6 000 years ago.
Opinion is divided as to why this mutation which allows some of us to drink milk took place. Some suggest that when our ancestors started to consume dairy produce, they built up a tolerance which altered their genes. Others think that the mutation happened before mammalian milk was drunk, and it allowed dairy consumption to take place.
But for people like me, it doesn’t really matter what came first. I want to know the health implications. After all, it’s drummed into us from an early age that milk is an essential part of our diet, chiefly because all that calcium is good for our bones.
“There are no serious health consequences of being lactose intolerant,” says Professor John Mayberry, a gastroenterologist at the University Hospitals of Leicester, “and you should remember that for much of the world it’s quite normal. There’s no increased risk of any diseases.”
You should also remember milk does not have a monopoly on calcium, which is found in broccoli, cabbage, soya beans and nuts. And just because you are lactose intolerant, it does not mean you have to give up cheese, as the fermentation process significantly reduces lactose levels.
Although Professor Mayberry confirms that my self-diagnosis is perfectly valid and safe, there are more medically rigorous tests you can take should you suspect lactose intolerance.
“Potentially, you can submit to a whole series of investigations,” says Professor Mayberry. “But the most simple and least invasive is the hydrogen breath test, in which the level of hydrogen in your breath is measured after you have drunk some lactose solution.”
The test is done at a hospital and you need a GP referral.
Hydrogen is one of the gases so charmingly emitted by the likes of me after drinking milk - bacteria in the gut produce hydrogen in reaction to unabsorbed food, and if your levels of hydrogen are 20 parts per million higher after drinking the lactose solution, then you’re lactose intolerant.
In my experience, that figure seems low. At times, I could have sworn I was expelling pure hydrogen.
Another common test is to measure the levels of glucose in your blood after drinking lactose. The lactase enzyme breaks down lactose into glucose - so if your glucose either rises slowly, or not at all after drinking lactose, it’s a sign of lactose intolerance.
Again, this hospital test needs a referral from your GP.
Although Professor Mayberry’s words are reassuring, for some, a lactose intolerance can actually be a symptom of something more serious.
A deficiency of lactase can be caused by inflammatory bowel diseases such as Crohn’s and ulcerative colitis, but as these also present other more serious symptoms such as weight loss, bleeding and mucus, a diagnosis of lactose intolerance alone is no reason to be alarmed.
But those who smugly think they can consume lactose for the rest of their lives should also think again. “Lactase starts to diminish in a lot of people in their 60s and 70s,” says Professor Mayberry, “which is why older people find they cannot eat certain food any more.
“Lactose isn’t just present in milk, but it’s used in all sorts of foods, such as whitener in loaves of bread.”
I’ve now started to reintroduce milk in a small way. I now take it in tea and coffee, and like many with lactose intolerance, I have just enough lactase in my small intestine to be able to cope with these amounts.
For the time being, I appear not to have passed on my intolerance to my children, who are both nearly in double figures, and seem able to drink milk with impunity.
But as soon as one of them emits a tell-tale burp, I’ll snatch the glass, and tell them to leave the rest of the herd. - Daily Mail